Overview (RELIABILITY command)

RELIABILITY estimates reliability statistics for the components of multiple-item additive scales. It uses any one of five models for reliability analysis and offers a variety of statistical displays. RELIABILITY can also be used to perform a repeated measures analysis of variance, a two-way factorial analysis of variance with one observation per cell, Tukey’s test for additivity, Hotelling’s T-square test for equality of means in repeated measures designs, and Friedman’s two-way analysis of variance on ranks. For more complex repeated measures designs, use the GLM procedure (available in the Advanced Models option).

Options

Model Type. You can specify any one of five models on the MODEL subcommand.

Statistical Display. Statistics available on the STATISTICS subcommand include descriptive statistics, correlation and covariance matrices, a repeated measures analysis of variance table, Hotelling’s T-square, Tukey’s test for additivity, Friedman’s chi-square for the analysis of ranked data, and Cochran’s Q.

Computational Method. You can force RELIABILITY to use the covariance method, even when you are not requesting any output that requires it, by using the METHOD subcommand.

Matrix Input and Output. You can read data in the form of correlation matrices and you can write correlation-type matrix materials to a data file using the MATRIX subcommand.

Basic Specification

The basic specification is VARIABLES and a variable list. By default, RELIABILITY displays the number of cases, number of items, and Cronbach’s alpha. Whenever possible, it uses an algorithm that does not require the calculation of the covariance matrix.

Subcommand Order

  • VARIABLES must be specified first.
  • The remaining subcommands can be named in any order.

Operations

  • STATISTICS and SUMMARY are cumulative. If you enter them more than once, all requested statistics are produced for each scale.
  • If you request output that is not available for your model or for your data, RELIABILITY ignores the request.
  • RELIABILITY uses an economical algorithm whenever possible but calculates a covariance matrix when necessary (see METHOD Subcommand (RELIABILITY command)).

Limitations

  • Maximum 1 VARIABLES subcommand.
  • Maximum 1 SCALE subcommand.
  • Maximum 10,000 variables on the VARIABLES subcommand.
  • Maximum 10,000 variables on the SCALE subcommand.